Speaking during a lecture at the IDF's National Security College, Barak said Israel might have to make "tough and crucial decisions" about its security.

"I am well aware of the difficulties involved in thwarting Iran's attempts to acquire a nuclear weapon," Barak said. "However, it is clear to me that without a doubt, dealing with the threat itself will be far more complicated, far more dangerous and far more costly in resources and human life."

Barak said that the events of the Arab Spring, which he said slowly turned into the "Islamic Summer", teach that at the moment of truth, Israel can only rely on itself.

Earlier Wednesday,Ayatollah Ali Khamenei, who has the final say on all state matters in Iran, voiced confidence that the Islamic Republic can beat the latest punitive measures aimed at blocking the country's vital oil and banking industries over the disputed program.

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"They (the West) explicitly say they need to increase pressures, tighten sanctions to force Iranian authorities to reconsider their calculations," Khamenei said in comments broadcast on state television. "But a look at the facts leads us not only to avoid reconsidering our calculations, but to move on our intended path with greater confidence."

The latest European Union sanctions against Iran's vital oil industry came into effect on July 1, three days after the U.S. tightened measures that prohibit international banks from completing oil transactions with Iranian banks. The moves, a response to Iran's refusal to suspend uranium enrichment, further complicate the country's ability to conduct trade abroad.

The West suspects Iran is pursuing a nuclear weapon. Iran says the program is for peaceful purposes such as power generation and medical treatment.

In his remarks, Khamenei said he felt some countries partaking in the U.S.-led sanctions will not continue them over the long term because of economic drawbacks, calling the sanctions a challenge that could be overcome.

"Although there are challenges in the path of the Iranian nation, there is no dead-end," he said.

Khamenei said Iran has offered some concessions in the past, but claimed the West is unwilling to allow what Iran calls a peaceful nuclear program.

He was referring to a period between 2003 and 2005 when Iran agreed under former reformist president Mohammad Khatami to suspend uranium enrichment and all related activities as part of confidence building measures to dispel fears that Tehran was not seeking nuclear weapons.

"The West became so arrogant during that period that they opposed possession of three centrifuges which our officials had agreed. But now there are 11,000 centrifuges operating in the country," he said.

Centrifuges are machines that spin at supersonic speed to purify uranium. Uranium enriched to low level is used to fuel a nuclear reactor but higher enrichment makes it suitable for use in building a nuclear weapon.

Iran's suspension of nuclear advancements coincided with a period of small steps toward easing the diplomatic freeze between Tehran and Washington, but tensions quickly returned following the election in 2005 of President Mahmoud Ahmadinejad and moves to restart Iran's nuclear efforts.

Ehud Barak.Tomer AppelbaumA worker in the nuclear power plant in Bushehr, Iran. AP

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